U.S. patent application number 10/288594 was filed with the patent office on 2003-05-15 for illumination system and projection system adopting the same.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Kim, Sung-ha, Sokolov, Kirill Sergeevich.
Application Number | 20030090632 10/288594 |
Document ID | / |
Family ID | 19715736 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030090632 |
Kind Code |
A1 |
Kim, Sung-ha ; et
al. |
May 15, 2003 |
Illumination system and projection system adopting the same
Abstract
An illumination system includes at least one light emitting
device to emit a light beam having different wavelengths, a
focusing lens to condense the light beam emitted from the light
emitting device, and a waveguide having an incident surface
inclined at a predetermined angle upon which the light beam
condensed by the focusing lens is incident. A projection system
includes at least one light emitting device to emit a light beam
having the different wavelengths, a focusing lens to condense the
light beam emitted from the light emitting device, a waveguide
having an incident surface inclined at a predetermined angle on
which the light beam is condensed by the focusing lens, a display
device to form an image by processing the light beam passing
through the waveguide according to an input image signal, and a
projection lens unit to magnify the image formed by the display
device and to project the magnified image toward a screen.
Inventors: |
Kim, Sung-ha; (Gyeonggi-do,
KR) ; Sokolov, Kirill Sergeevich; (Gyeonggi-do,
KR) |
Correspondence
Address: |
STAAS & HALSEY LLP
700 11TH STREET, NW
SUITE 500
WASHINGTON
DC
20001
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
Suwon-City
KR
|
Family ID: |
19715736 |
Appl. No.: |
10/288594 |
Filed: |
November 6, 2002 |
Current U.S.
Class: |
353/31 |
Current CPC
Class: |
G02B 27/0905 20130101;
G02B 27/0944 20130101; G02B 6/4214 20130101; G02B 6/4215 20130101;
G02B 27/0994 20130101; G02B 27/286 20130101 |
Class at
Publication: |
353/31 |
International
Class: |
G03B 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2001 |
KR |
2001-68816 |
Claims
What is claimed is:
1. An illumination system comprising: a light emitting device to
emit a light beam having a wavelength; a holographic optical
element to change an optical path of the light beam emitted from
the light emitting device; and a waveguide to receive the light
beam from the holographic optical element and to guide the received
light beam.
2. The illumination system as claimed in claim 1, wherein the light
emitting device has an array structure.
3. The illumination system as claimed in claim 2, wherein the light
emitting device is a light emitting diode (LED), a laser diode, an
organic electro luminescent (EL), or a field emission display
(FED).
4. The illumination system as claimed in claim 3, further
comprising a prism array to receive the guided light beam from the
waveguide and to make parallel the received light beam so that the
parallel light beam proceeds in one direction.
5. The illumination system as claimed in claim 4, wherein the
holographic optical element is arranged at a first or second end
portion of the waveguide.
6. The illumination system as claimed in claim 5, further
comprising a parallel beam forming unit to make parallel the light
beam emitted from the light emitting device.
7. The illumination system as claimed in claim 6, wherein the
parallel beam forming unit is a collimating lens array or a Fresnel
lens array.
8. The illumination system as claimed in claim 5, further
comprising an optical path changer to receive the parallel light
beam from the prism array and to change a proceeding path of the
received light beam.
9. The illumination system as claimed in claim 8, wherein a
plurality of the light emitting devices are arranged in a line.
10. The illumination system as claimed in claim 9, wherein the
optical path changer is a dichroic filter to reflect or transmit
the light beam passing through the prism array according to the
wavelength thereof.
11. The illumination system as claimed in claim 9, wherein the
optical path changer is a cholesteric band modulation filter to
reflect or transmit the light beam passing through the prism array
according to a polarization direction and the wavelength of the
light beam.
12. The illumination system as claimed in claim 11, wherein the
cholesteric band modulation filter comprises: a first mirror
surface to reflect the light beam of a right circular polarization
and to transmit a light beam of a left circular polarization, and a
second mirror surface to transmit the light beam of a right
circular polarization and to reflect the light beam of a left
circular polarization according to the wavelength of the light
beam.
13. The illumination system as claimed in claim 9, wherein the
light emitting device, the holographic optical element, and the
waveguide are arranged in a multiple layer structure.
14. The illumination system as claimed in claim 8, further
comprising a plurality of the light emitting devices separated at
an angle.
15. The illumination system as claimed in claim 14, wherein the
optical path changer is an X prism or X type dichroic filter.
16. The illumination system as claimed in claim 14 wherein the
light emitting device, the holographic optical element, and the
waveguide are arranged in a multiple layer structure.
17. The illumination system as claimed in claim 4, wherein the
prism array is formed integrally with the waveguide at an exit end
portion of the waveguide.
18. An illumination system comprising: a plurality of light
emitting devices to emit light beams having different wavelengths;
a plurality of holographic optical elements, corresponding to the
light emitting devices, to change optical paths of the light beams
emitted from the light emitting devices; and a waveguide to guide
light beams incident from the holographic optical elements in a
same direction.
19. The illumination system as claimed in claim 18, wherein the
light emitting devices have an array structure.
20. The illumination system as claimed in claim 18, wherein each of
the light emitting devices is a light emitting diode (LED), a laser
diode, an organic electro luminescent (EL), or a field emission
display (FED).
21. The illumination system as claimed in claim 20, further
comprising a prism array to receive the guided light beam from the
waveguide and to make the light beam parallel so that the parallel
light beam proceeds in one direction.
22. The illumination system as claimed in claim 21, wherein the
prism array is formed integrally with the waveguide at an exit
portion of the waveguide.
23. The illumination system as claimed in claim 20, wherein the
holographic optical element is arranged at a first or second end
portion of the waveguide.
24. The illumination system as claimed in claim 23, further
comprising a parallel beam forming unit to make parallel the light
beam emitted from each of the light emitting devices.
25. The illumination system as claimed in claim 24, wherein the
parallel beam forming unit is a collimating lens array or Fresnel
lens array.
26. An illumination system comprising: a light emitting device to
emit a light beam having different wavelengths; a focusing lens to
condense the light beam emitted from the light emitting device; and
a waveguide having an inclined incident surface, upon which the
condensed light is incident.
27. The illumination system as claimed in claim 26, wherein the
light emitting device has an array structure.
28. The illumination system as claimed in claim 27, wherein the
light emitting device is a light emitting diode (LED), a laser
diode, an organic electro luminescent (EL), or a field emission
display (FED).
29. The illumination system as claimed in claim 28, further
comprising a first parallel beam forming unit to make parallel the
light beam emitted from the light emitting device.
30. The illumination system as claimed in claim 29, further
comprising a second parallel beam forming unit to receive the
incident light after the incident light has passed through the
waveguide and to make parallel the received light beam.
31. The illumination system as claimed in claim 30, wherein the
first and second parallel beam forming units are collimating lens
arrays or Fresnel lens arrays.
32. The illumination system as claimed in claim 31, further
comprising an optical path changer to change a proceeding path of
the light beam passing through the second parallel beam forming
unit by selectively transmitting or reflecting the light beam.
33. The illumination system as claimed in claim 32, further
comprising a plurality of the light emitting devices arranged in a
line.
34. The illumination system as claimed in claim 33, wherein the
optical path changer is a dichroic filter to reflect or transmit
the light beam passing through the second parallel beam forming
unit according to the wavelength thereof.
35. The illumination system as claimed in claim 33, wherein the
optical path changer is a cholesteric band modulation filter to
reflect or transmit the light beam passing through the second
parallel beam forming unit according to a polarization direction
and the wavelength thereof.
36. The illumination system as claimed in claim 35, wherein the
cholesteric band modulation filter comprises: a first mirror
surface to reflect the light beam of a right circular polarization
and to transmit the light beam of a left circular polarization, and
a second mirror surface to transmit the light beam of the right
circular polarization and to reflect the light beam of the left
circular polarization according to the wavelength of the light
beam.
37. The illumination system as claimed in claim 32, wherein a
plurality of the light emitting devices are separated at an
angle.
38. The illumination system as claimed in claim 37, wherein the
optical path changer is an X prism or an X type dichroic
filter.
39. The illumination system as claimed in claim 37, wherein the
light emitting device, the focusing lens, and the waveguide are
arranged in a multiple layer structure.
40. The illumination system as claimed in claim 39, wherein the
multiple layer structure is a symmetrical structure.
41. The illumination system as claimed in claim 33, wherein the
light emitting device, the focusing lens, and the waveguide are
arranged in a multiple layer structure.
42. An illumination system comprising: a plurality of light
emitting devices to emit a plurality of light beams having
different wavelengths; a diffractive optical element to change an
optical path of the light beams emitted from the light emitting
devices; and a waveguide to guide the light beams which have passed
through the diffractive optical element.
43. The illumination system as claimed in claim 42, wherein the
light emitting devices have an array structure.
44. The illumination system as claimed in claim 43, wherein the
light emitting devices are a light emitting diode (LED), a laser
diode, an organic electro luminescent (EL), or a field emission
display (FED).
45. The illumination system as claimed in claim 44, further
comprising a prism array to receive the guided light beams from the
waveguide to make parallel the received light beams so that the
parallel light beams proceed in one direction.
46. The illumination system as claimed in claim 45, further
comprising a parallel beam forming unit to make parallel the light
beams emitted from the light emitting devices.
47. The illumination system as claimed in claim 46, wherein the
parallel beam forming unit is a collimating lens array or Fresnel
lens array.
48. A projection system comprising: a plurality of light emitting
devices to emit a plurality of light beams having different
wavelengths; a holographic optical element to change a proceeding
path of the light beams emitted from the light emitting devices; a
waveguide to guide the light beams passing through the holographic
optical element; a display device to form an image by processing
the light beams passing through the waveguide according to an input
image signal; a screen; and a projection lens unit to magnify the
image formed by the display device and to project the magnified
image toward the screen.
49. The projection system as claimed in claim 48, wherein the light
emitting devices have an array structure.
50. The projection system as claimed in claim 49, wherein the light
emitting devices are a light emitting diode (LED), a laser diode,
an organic electro luminescent (EL), or a field emission display
(FED).
51. The projection system as claimed in claim 50, further
comprising a prism array to receive the guided light beams from the
waveguide and to make parallel the received light beams.
52. The projection system as claimed in claim 51, wherein the prism
array is formed integrally with the waveguide at an exit end
portion of the waveguide.
53. The projection system as claimed in claim 52, further
comprising: a fly eye lens to receive the parallel light beams from
the prism array and to make uniform an intensity of the received
light beams; and a relay lens to condense the uniform light beams
which have passed through the fly eye lens on the display
device.
54. The projection system as claimed in claim 53, further
comprising a parallel beam forming unit to make parallel the light
beams emitted from the light emitting devices.
55. The projection system as claimed in claim 54, wherein the
parallel beam forming unit is a collimating lens array or a Fresnel
lens array.
56. The projection system as claimed in claim 52, further
comprising an optical path changer to receive the parallel light
beams from the prism array and to change a proceeding path of the
received light beams.
57. The projection system as claimed in claim 56, further
comprising: a fly eye lens to receive the parallel light beams from
the prism array and to make uniform an intensity of the received
light beams; and a relay lens to condense the uniform intensity
light beams from the fly eye lens on the display device.
58. A projection system comprising: a plurality of light emitting
devices to emit a plurality of light beams having different
wavelengths; a focusing lens to condense the light beams emitted
from the light emitting devices; a waveguide having an inclined
surface upon which the condensed light is incident; a display
device to form an image by processing the light beams passing
through the waveguide according to an input image signal; a screen;
and a projection lens unit to magnify the image formed by the
display device and to project the magnified image toward a
screen.
59. The projection system as claimed in claim 58, wherein the light
emitting devices have an array structure.
60. The projection system as claimed in claim 59, wherein the light
emitting devices are a light emitting diode (LED), a laser diode,
an organic electro luminescent (EL), or a field emission display
(FED).
61. The projection system as claimed in claim 60, further
comprising a first parallel beam forming unit to make parallel the
light beams emitted from the light emitting devices.
62. The projection system as claimed in claim 61, further
comprising a second parallel beam forming unit to make parallel the
light beams passing through the waveguide.
63. The projection system as claimed in claim 62, further
comprising: a fly eye lens to make uniform a strength of the light
beams emitted from the second parallel beam forming unit uniform;
and a relay lens to condense the light beams passing through the
fly eye lens on the display device.
64. The projection system as claimed in claim 63, further
comprising: an optical path changer, provided between the second
parallel beam forming unit and the fly eye lens, to change a
proceeding path of the light beams passing through the second
parallel beam forming unit by selectively transmitting or
reflecting the light beams.
65. The projection system as claimed in claim 62, wherein the first
and second parallel beam forming units are collimating lens arrays
or Fresnel lens arrays.
66. A projection system comprising: a plurality of light emitting
devices to emit light beams having different wavelengths; a
plurality of holographic optical elements to change respective
proceeding paths of the light beams emitted from the light emitting
devices; a waveguide to guide the light beams input through the
holographic optical elements to proceed in a same direction; a
display device to form an image by processing the light beam
passing through the waveguide according to an input image signal; a
screen; and a projection lens unit to magnify the image formed by
the display device and to project the magnified image towards the
screen.
67. The projection system as claimed in claim 66, wherein the light
emitting device has an array structure.
68. The projection system as claimed in claim 67, wherein the light
emitting device is a light emitting diode (LED), a laser diode, an
organic electro luminescent (EL), or a field emission display
(FED).
69. The projection system as claimed in claim 68, further
comprising a prism array to receive the guided light beam from the
waveguide and to make parallel the received light beam.
70. The projection system as claimed in claim 69, wherein the prism
array is formed integrally with the waveguide at an exit portion of
the waveguide.
71. The projection system as claimed in claim 69, further
comprising: a fly eye lens to make uniform an intensity of the
parallel light beam of the prism array; and a relay lens to
condense the uniform light beam of the fly eye lens on the display
device.
72. An illumination system comprising: a light emitting device to
emit a light beam having a wavelength; a light receiving element to
reduce a cross section of the light beam emitted from the light
emitting device; and a waveguide to receive the reduced light beam
from the light receiving element and to guide the received light
beam.
73. The illumination system as claimed in claim 72, wherein the
light receiving element is a holographic optical element to change
an optical path of the light beam emitted from the light emitting
device.
74. The illumination system as claimed in claim 72, further
comprising a plurality of the light emitting devices arranged in an
array.
75. The illumination system as claimed in claim 72, wherein the
light receiving element is a focusing lens to condense the light
beam emitted from the light emitting device.
76. The illumination system as claimed in claim 72, further
comprising a prism to receive the guided light beam from the
waveguide and to make parallel the received light beam so that the
parallel light beam proceeds in one direction.
77. The illumination system as claimed in claim 72, wherein the
prism is an end portion of the waveguide comprising a first prism
surface having first and second inclined surfaces.
78. The illumination system as claimed in claim 77, wherein the
prism further comprises a second prism surface having third and
fourth inclined surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Application
No. 2001-68816, filed Nov. 6, 2001, in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an illumination system and
a projection system adopting the same, and more particularly, to an
illumination system which can realize a color image without a color
wheel, and a projection system adopting the same.
[0004] 2. Description of the Related Art
[0005] Referring to FIG. 1, a conventional projection system
includes a light source 100, a first relay lens 102 to condense the
light beam emitted from the light source 100, a color wheel 105 to
split light beams incident from the first relay lens 102 into R, G
and B color light beams, a fly eye lens 107 to make the light beam
passing through the color wheel 105 uniform, a second relay lens
110 to condense the light beam passing through the fly eye lens
107, a display device 112 to form a color image from the R, G and B
color light beams sequentially input through the color wheel 105,
and a projection lens system 115 to make an image formed by the
display device 112 proceed toward a screen 118.
[0006] A xenon lamp, a metal-halide lamp, or a UHP lamp is used as
the light source 100. These lamps emit too much unnecessary
infrared and ultraviolet energy. Accordingly, since much heat is
generated, a cooling fan is used to cool the system. However, the
cooling fan also acts as a noise source. Also, since the spectrum
of the lamp light source is widely distributed across many
wavelengths, due to a narrow color gamut, the selection of color is
limited, color purity is inferior, and the life span is short.
Thus, long-term use of the lamp is not possible.
[0007] In the conventional projection system, to realize a color
image, the color wheel 105 is rotated by driving a motor (not
shown) at a high speed so that R, G and B color light beams are
sequentially illuminated onto the display device 112. R, G and B
color filters are equally arranged on the entire surface of the
color wheel 105. The color wheel 105 rotates three turns for each
image. The three colors are sequentially used, but only one color
is used for each rotation, thus, 2/3 of the light is lost. Also,
more light is lost at a boundary portion between neighboring color
filters.
[0008] Furthermore, since the color wheel 105 rotates at a high
speed, noise is generated. Also, the mechanical movement of the
driving motor has an adverse effect on stability. Further, due to
mechanical limitations of the driving motor, it is difficult to
obtain a speed over certain ranges and a color breakup phenomenon
occurs. Also, since the price of the color wheel is very high, the
manufacturing cost increases.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is an object of the present invention to
provide an illumination system capable of forming a color image
without a color wheel by using a light emitting device to emit a
light beam having a predetermined wavelength so that color purity
and color gamut is improved, and a projection system adopting the
illumination system.
[0010] It is another object of the present invention to provide an
illumination system having at least one waveguide to guide a light
beam without loss of light with a reduced cross section of the
light beam, so that the volume of the system is reduced and the
efficiency of the lighting improves, and a projection system
adopting the illumination system.
[0011] Additional objects and advantages of the invention will be
set forth in part in the description which follows and, in part,
will be obvious from the description, or may be learned by practice
of the invention.
[0012] The foregoing and additional objects of the present
invention are achieved by providing a light emitting device to emit
a light beam having a wavelength; a holographic optical element to
change an optical path of the light beam emitted from the light
emitting device; and a waveguide to receive the light beam from the
holographic optical element and to guide the received light
beam.
[0013] The light emitting device may have an array structure, and
the light emitting device may be a light emitting diode (LED), a
laser diode, an organic electro luminescent (EL), or a field
emission display (FED).
[0014] The illumination system may further include a prism array to
make the light beam passing through the waveguide proceed in a
single parallel direction.
[0015] The holographic optical element may be arranged at an upper
or a lower portion of the waveguide.
[0016] The illumination system may further include a parallel beam
forming unit to make parallel the light beam emitted from the light
emitting device or light emitting device array.
[0017] The parallel beam forming unit may be a collimating lens
array or Fresnel lens array.
[0018] The illumination system may further include an optical path
changer to change a path of the light beam passing through the
prism array.
[0019] A plurality of the light emitting devices or the light
emitting device arrays may be horizontally arranged in a line.
[0020] The optical path changer may be a dichroic filter to reflect
or transmit the light beam passing through the prism array
according to the wavelength thereof.
[0021] The optical path changer may be a cholesteric band
modulation filter to reflect or transmit the light beam passing
through the prism array according to the polarization direction and
wavelength thereof.
[0022] The cholesteric band modulation filter may have a first
mirror surface to reflect a light beam of right circular
polarization and to transmit a light beam of left circular
polarization, and a second mirror surface to transmit the light
beam of right circular polarization and reflect the light beam of
left circular polarization, with respect to a light beam having a
predetermined wavelength.
[0023] The light emitting device or light emitting device array,
the holographic optical element, and the waveguide may be further
arranged in a multiple layer structure.
[0024] A plurality of the light emitting devices or light emitting
device arrays may be separated at a predetermined angle.
[0025] The optical path changer may be an X prism or X type
dichroic filter.
[0026] According to an aspect of the present invention, the light
emitting device or light emitting device array, the holographic
optical element, and the waveguide may be arranged in a multiple
layer structure.
[0027] The prism array may be formed integrally with the waveguide
at an exit end portion of the waveguide.
[0028] The foregoing and other objects of the present invention may
also be achieved by providing a light emitting device to emit a
light beam having a wavelength; a holographic optical element to
change an optical path of the light beam emitted from the light
emitting device; and a waveguide to receive the light beam from the
holographic optical element and to guide the received light
beam.
[0029] The foregoing and other objects of the present invention may
also be achieved by providing a plurality of light emitting devices
to emit light beams having different wavelengths; a plurality of
holographic optical elements, corresponding to the light emitting
devices, to change optical paths of the light beams emitted from
the light emitting devices; and a waveguide to guide light beams
incident from the holographic optical elements in a same
direction.
[0030] The foregoing and other objects of the present invention may
also be achieved by providing a light emitting device to emit a
light beam having different wavelengths; a focusing lens to
condense the light beam emitted from the light emitting device; and
a waveguide having an inclined incident surface, upon which the
condensed light is incident.
[0031] The foregoing and other objects of the present invention may
also be achieved by providing a light emitting device to emit a
light beam having different wavelengths; a diffractive optical
element to change an optical path of the light beam emitted from
the light emitting device; and a waveguide to guide the light beam
which has passed through the diffractive optical element.
[0032] The foregoing and other objects of the present invention may
also be achieved by providing a light emitting device to emit a
light beam having different wavelengths; a holographic optical
element to change a proceeding path of the light beam emitted from
the light emitting device; a waveguide to guide the light beam
passing through the holographic optical element; a display device
to form an image by processing the light beam passing through the
waveguide according to an input image signal; a screen; and a
projection lens unit to magnify the image formed by the display
device and to project the magnified image toward the screen.
[0033] According to an aspect of the present invention, the above
projection system may further include a fly eye lens to make
uniform the strength of the light beam emitted from the second
parallel beam forming unit, and a relay lens to condense the light
beam passing through the fly eye lens on the display device.
[0034] The foregoing and other objects of the present invention may
be achieved by providing a display device to form an image by
processing the light beam passing through the waveguide according
to an input image signal; a screen; and a projection lens unit to
magnify the image formed by the display device and to project the
magnified image towards the screen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] These and other objects and advantages of the invention will
become apparent and more readily appreciated from the following
description of the preferred embodiments, taken in conjunction with
the accompanying drawings of which:
[0036] FIG. 1 is a view showing the structure of a conventional
projection system;
[0037] FIG. 2 is a front view of an illumination system according
to a first embodiment of the present invention;
[0038] FIGS. 3A through 3C are views showing various examples of
waveguides used in the illumination system of FIG. 2;
[0039] FIG. 4 is a plan view of the illumination system of FIG.
2;
[0040] FIG. 5 is a view showing the structure of an illumination
system according to a second embodiment of the present
invention;
[0041] FIGS. 6 through 8 are views showing various examples of an
optical path changer used in the illumination systems of the
present invention;
[0042] FIG. 9 is a view showing the structure of an illumination
system according to a third embodiment of the present invention;
and
[0043] FIG. 10 is a view showing the structure of a projection
system adopting the illumination system according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Reference will now be made in detail to the present
preferred embodiments of the present invention, examples of which
are illustrated in the accompanying drawings, wherein like
reference numerals refer to like elements throughout.
[0045] Referring to FIG. 2, an illumination system according to a
first embodiment of the present invention includes at least one
light emitting device 10 to emit a light beam having a
predetermined wavelength, a holographic optical element 15 to
change a proceeding path of the light beam emitted from the light
emitting device 10, and a waveguide 20 to guide the light beam
passing through the holographic optical element 15.
[0046] An LED (light emitting diode), an LD (laser diode), an
organic EL (electro luminescent), or an FED (field emission
display) may be used as the light emitting device 10. Also, an
array structure in which the light emitting devices 10 are arranged
in a 2-dimensional array may be used. The light emitting device 10
or the light emitting device array can be formed to emit light
beams having different wavelengths. For example, as shown in FIG.
4, the light emitting device 10 or the light emitting device array
may include a first light emitting device 10a to emit a light beam
having a red (R) wavelength, a second light emitting device 10b to
emit a light beam having a green (G) wavelength, and a third light
emitting device 10c to emit a light beam having a blue (B)
wavelength.
[0047] A parallel beam forming unit 13, such as a collimating lens
array or a Fresnel lens array, to make parallel the light beams
emitted from the light emitting devices 10 or light emitting device
arrays 10a, 10b, and 10c can be further provided. The holographic
optical element 15 makes the parallel light beams from the parallel
beam forming unit 13 incident on the waveguide 20 at a
predetermined angle. The incident light beam is totally reflected
inside the waveguide 20. The holographic optical element 15
diffracts the light beam incident on the waveguide 20 at a
predetermined angle so that a cross section of the light beam is
reduced inside the waveguide 20. That is, it can be seen that the
cross section of a light beam proceeding inside the waveguide 20
after passing through the holographic optical element 15 is reduced
as compared to the cross section of the light beam incident on the
holographic optical element 15. Therefore, not only the volume of
the illumination system, but also loss of light can be reduced.
[0048] The holographic optical element 15 can be installed at the
upper or lower portion of the waveguide 20. However, when the light
beam passing through the holographic optical element 15 and
starting from one end portion of the waveguide 20 is totally
reflected by a lower surface of the waveguide 20, and incident on
an upper surface thereof, a diffraction angle or the length of the
holographic optical element 15 must be adjusted so as not to be
reflected back to the holographic optical element 15. The
holographic optical element 15 can be replaced by a diffractive
optical element having the same function.
[0049] Also, a prism array 25 to make parallel light beams passing
through the waveguide 20 and proceeding in different directions is
arranged at an end portion of an exit side of the waveguide 20.
That is, the light beams coming out of the waveguide 20 in
different directions from one another are condensed by the prism
array 25 to proceed in one direction. Although the prism array 25
is separate from the waveguide 20 in the described embodiment, the
prism array 25 can be integrally formed at the exit side portion of
the waveguide 20. Alternatively, as shown in FIG. 3A, the end
portion of the exit side of the waveguide 20 can be formed to have
a surface 26 inclined at a predetermined angle which performs the
same function as the prism array 25. Also, as shown in FIGS. 3B and
3C, the waveguide 20 can be formed such that the end portion of the
exit side of the waveguide 20 has at least one prism surface 27 or
28. Accordingly, the light beams proceeding in different directions
are received by the waveguide 20 and proceed in a single direction
after passing through the waveguide. Thus, the light beam emitted
from the light emitting device 10 passes through the prism arrays
25, 26, 27 and 28 while the cross section of the light beam is
reduced by the waveguide 20.
[0050] Furthermore, to secure a sufficient amount of light, the
light emitting device 10 or light emitting device array is provided
in multiple numbers. Also, additional holographic optical elements
15' and waveguides 20' can be provided. Here, the waveguides 20 and
20' are arranged to have a step shape on a different plane from
that on which a neighboring waveguide 20 is disposed, so that
proceeding paths of the light beams passing through the waveguides
20 and 20' do not disturb each other.
[0051] Meanwhile, an optical path changer 30 to change a proceeding
path of the light beam passing through the prism array 25, 26, 27,
or 28 can be further provided. A detailed example of the optical
path changer 30 will be described later.
[0052] Referring to FIG. 5, an illumination system according to a
second embodiment of the present invention includes at least one
light emitting device or light emitting device array 40, a
waveguide 50 to guide a proceeding path of a light beam, and a
focusing lens 45 to condense a light beam toward an input end
portion of the waveguide 50. An LED (light emitting diode), an LD
(laser diode), an organic EL (electro luminescent), or an FED
(field emission display) can be used as the light emitting device
or light emitting device array 40.
[0053] An input end portion of the waveguide 50 has a surface 48
inclined at a predetermined angle so that a light beam condensed by
the focusing lens 45 is totally reflected in the waveguide 50. As
an example, the surface 48 may be inclined at about 45.degree..
Here, since the light beam is condensed at a point of the input end
portion of the waveguide 50 by the focusing lens 45, the cross
section of the light beam passing through the waveguide 50 can be
further reduced.
[0054] Also, the light emitting device or light emitting device
array 40 can be provided in multiple numbers and arranged linearly.
Here, the focusing lenses 45, 45' and 45" corresponding to the
respective light emitting devices or light emitting device arrays
40 are arranged on different planes in a step-like form. The light
beams condensed by the focusing lenses 45, 45' and 45" are
respectively guided by waveguides 50, 50', and 50" disposed on
different planes. As a result, a sufficient amount of light can be
transmitted. While the light emitting devices or light emitting
device arrays 40 are arranged linearly, light emitting devices or
light emitting device arrays 40 emitting light beams having
different wavelengths can be formed as above.
[0055] A first parallel beam forming unit 43 to make parallel the
light beam emitted from the light emitting device or light emitting
device array 40 is provided between the light emitting device or
light emitting device array 40 and the focusing lenses 45, 45' and
45". A second parallel beam forming unit 55 to make parallel the
light beams emitted from the waveguides 50, 50', and 50" is
provided at the exit end portions of the waveguides 50, 50', and
50". The first and second parallel beam forming units 43 and 55 may
be collimating lens arrays or Fresnel lens arrays. Here, an optical
path changer 58 to change a proceeding path of the light beam
passing through the second parallel beam forming unit 55 can be
further provided.
[0056] FIGS. 6 through 8 show various examples of the optical path
changers 30 and 58. Here, although the examples of the optical path
changers 30 and 58 can be applied to first and second embodiments,
reference numerals in the first embodiment of the present invention
will be used in the following description.
[0057] The light emitting device and light emitting device array 10
can be formed of the first, second, and third light emitting
devices and light emitting device arrays 10a, 10b, and 10c
respectively emitting light beams having R, G, and B wavelengths,
and can be arranged linearly in a horizontal direction, as shown in
FIGS. 6 and 7. Also, to secure a sufficient amount of light, the
first, second, and third light emitting devices and light emitting
device arrays 10a, 10b, and 10c can be provided further in multiple
numbers. The light emitting devices and light emitting device
arrays 10a, 10b, and 10c can be arranged in multiple layers in a
vertical direction, in addition to the arrangement in a horizontal
direction. When the light emitting devices and light emitting
device arrays 10a, 10b, and 10c are provided in multiple numbers,
the holographic optical element 15, the focusing lens 45, or the
waveguides 20 and 50 are provided in corresponding multiple
numbers. In the case of a multiple layer structure, layers having
the light emitting device 10, the holographic optical element 15 or
the focusing lens 45, and the waveguides 20 and 50 are arranged to
face one another. The light emitting device or light emitting array
corresponding to each wavelength can be formed by repeating the
same horizontal structure or multiple layer structure.
[0058] The optical path changers 30 and 58 selectively transmit or
reflect light beams incident in different directions to proceed
along the same optical path. The optical path changers 30 and 58
can be formed of first, second, and third dichroic filters 30a,
30b, and 30c, each reflecting or transmitting the light beams from
the first through third light emitting devices or light emitting
device arrays 10a, 10b, and 10c according to the wavelength
thereof, as shown in FIG. 6. For example, a light beam having an R
wavelength is emitted from the first light emitting device or light
emitting device array 10a, a light beam having a G wavelength is
emitted from the second light emitting device or light emitting
device array 10b, and a light beam having a B wavelength is emitted
from the third light emitting device or light emitting device array
10c.
[0059] The first dichroic filter 30a reflects only the light beam
having the R wavelength and transmits the other light beams having
the G and B wavelengths. The second dichroic filter 30b reflects
only the light beam having the G wavelength and transmits the other
light beams having the R and B wavelengths. The third dichroic
filter 30c reflects only the light beam having the B wavelength and
transmits the other light beams having the R and G wavelengths.
Thus, when the light beam passing through the prism array 25 is
incident on the first dichroic filter 30a, the light beam is
reflected in a direction indicated by the `A` arrows shown in FIG.
6. When the G light beam passing through the prism array 25 is
incident on the second dichroic filter 30b, the light beam is
reflected by the second dichroic filter 30b and passes through the
first dichroic filter 30b and proceeds in the `A` direction . Also,
when the B light beam passing through the prism array 25 is
incident on the third dichroic filter 30c, the light beam is
reflected by the third dichroic filter 30c and passes through the
second and first dichroic filters 30b and 30a and proceeds in the
`A` direction . As a result, the R, G, and B color light beams
traveling along different paths can proceed along the same
path.
[0060] Alternately, a cholesteric band modulation filter 35 to
selectively reflect or transmit an incident light beam according to
the polarization direction of the light beam can be used as the
optical path changer, as shown in FIG. 7. With respect to a light
beam having a predetermined wavelength, the cholesteric band
modulation filter 35, for example, can change an optical path by
reflecting a light beam of right circular polarization and
transmitting a light beam of left circular polarization, or
reversely, by transmitting the light beam of right circular
polarization and reflecting the light beam of left circular
polarization. The cholesteric band modulation filter 35 can be
formed of first, second and third cholesteric band modulation
filters 35a, 35b, and 35c which selectively transmit or reflect R,
G, and B color light beams according to the polarization direction
of each light beam.
[0061] To improve the efficiency of light by using both light beams
of right polarization and left polarization, each of the first
through third cholesteric band modulation filters 35a, 35b, and 35c
includes a first mirror surface 37 to reflect a light beam of right
polarization and transmit a light beam of left polarization, and a
second mirror surface 38 to transmit the light beam of right
polarization and reflect the light beam of left polarization, with
respect to the wavelength corresponding to each filter. Here, the
light beam of right circular polarization and the light beam of
left circular polarization are indicated by + and -, respectively.
For example, R+ denotes an R light beam of right circular
polarization and R- denotes an R light beam of left circular
polarization.
[0062] The R, G, and B color light beams passing through the light
emitting device or light emitting device array 10 proceed toward
the first, second, and third cholesteric band modulation filters
35a, 35b, and 35c, respectively. In the first, second, and third
cholesteric band modulation filters 35a, 35b, and 35c, the first
and second mirror surfaces 37 and 38 are provided in a diagonal
direction with respect to a direction in which the light beam is
input. Here, an example of a proceeding path of the R light beam
will be described. When an R+ light beam of the R light beam
passing through the prism array 25 first meets the first mirror
surface 37, the light beam is reflected by the first mirror surface
37. Then, when the R+ light beam meets the second mirror surface
38, the light beam passes through the second mirror surface 38 to
proceed in the `A` direction. Also, when the R+ light beam first
meets the second mirror surface 38, the light beam passes through
the second mirror surface 38 and is reflected by the first mirror
surface 37 to proceed in the `A` direction. When an R- light beam
of the R light beam passing through the prism array 25 first meets
the first mirror surface 37, the light beam passes through the
first mirror surface 37. Then, when the R- light beam meets the
second mirror surface 38, the light beam is reflected by the second
mirror surface 38 to proceed in the `A` direction.
[0063] The above operation is equally applied to the G+ and G-
light beams and the B+ and B- light beams so that all of the light
beams proceed in the same direction (`A`). The first, second, and
third cholesteric band modulation filters 35a, 35b, and 35c perform
selective transmission or reflection operations with respect to
only a light beam having a corresponding wavelength and transmit
all of the other light beams having different wavelengths
regardless of the polarization direction. Since both the light
beams of right circular polarization and left circular polarization
can be effectively used, the efficiency is very high.
[0064] Alternately, the optical path changer can be formed of an X
prism 60 or X type dichroic filter film, as shown in FIG. 8. Here,
the first, second, and third light emitting devices or light
emitting device arrays 10a, 10b, and 10c are arranged to be
separated from one another at a predetermined angle with respect to
the X prism 60 or the X type dichroic filter film. The X prism 60
includes first, second, and third incident surfaces 61, 62, and 63
disposed to face the first, second, and third light emitting
devices or light emitting device arrays 10a, 10b, and 10c, the
holographic optical element 15, and the waveguide 20, and one exit
surface 64. Also, the X prism 60 includes third and fourth mirror
surfaces 60a and 60b, which are formed to cross each other to
change an optical path by selectively transmitting or reflecting an
incident light beam according to the wavelength of the light beam.
For example, the third mirror surface 60a reflects an R light beam
while transmitting G and B light beams. The fourth mirror surface
60b reflects the B light beam while transmitting the R and G light
beams.
[0065] The R, G, and B color light beams emitted from the first
through third light emitting devices or light emitting device
arrays 10a, 10b, and 10c and passing through the holographic
optical element 15, the waveguide 20, and the prism arrays 25, 26,
27, and 28 are incident on the corresponding first through third
incident surfaces 61, 62, and 63 of the X prism 60. The R, G, and B
color light beams input along different paths are transmitted
through or reflected by the third and fourth mirror surfaces 60a
and 60b to proceed in the same direction through the exit surface
64.
[0066] According to the above-described embodiments, the light
emitting devices or light emitting device arrays 10a, 10b, and 10c
can be arranged in various ways, or one of the optical path
changers 30, 35, and 60 suitable for the arrangement of the light
emitting devices or light emitting device arrays 10a, 10b, and 10c
can be selected and arranged. Also, the above-described holographic
optical element 15 can be replaced by at least one diffractive
optical element having the same function. Further, in the second
embodiment, one of the dichroic filter, the cholesteric band
modulation filter, the X prism, and the X type dichroic filter film
can be selected and used.
[0067] The third embodiment of the present invention, as shown in
FIG. 9, includes fourth, fifth and sixth light emitting devices or
light emitting device arrays 65, 66, and 67 to emit the R, G, and B
color light beams, a parallel beam forming unit 70 to make parallel
the light beams emitted from the fourth, fifth and sixth light
emitting devices or light emitting device arrays 65, 66, and 67,
fourth through sixth holographic optical elements 75, 76 and 77 to
change the optical path of each of the R, G, and B color light
beams at a predetermined angle, a waveguide 80 to totally reflect
and pass the incident light beam passing through the holographic
optical elements 75, 76, and 77, and a prism array 85 provided at
an exit end portion of the waveguide 80.
[0068] The parallel beam forming unit 70 may be a Fresnel lens
array or a collimating lens array. The R, G, and B color light
beams emitted from the parallel beam forming unit 70 to be parallel
to one another are incident on the waveguide 80 to be totally
reflected, after passing through the corresponding fourth through
sixth holographic optical elements 75, 76, and 77. Since the prism
array 85 is integrally formed at the exit end portion of the
waveguide 80, the light beams proceeding in different directions
through the waveguide 80 are emitted in one direction to be
parallel to one another. The prism array 85 can be formed
integrally with the waveguide 80 or provided separately from the
waveguide 80. Also, to secure a sufficient amount of light, light
emitting devices or light emitting device arrays 65', 66', and 67'
can be further provided. A parallel beam forming unit 70',
holographic optical elements 75', 76', and 77', a waveguide 80',
and a prism array 85', which correspond to the light emitting
devices or light emitting device arrays 65', 66', and 67', are
further provided in the same structure as described above. Here,
the holographic optical elements 75', 76', and 77' and the
waveguide 80' are arranged on a plane different from a plane of the
holographic optical elements 75, 76, and 77 and the waveguide 80,
so that optical paths thereof do not overlap.
[0069] According to the third embodiment of the present invention,
as the R, G, and B color light beams are emitted from the fourth
through sixth light emitting devices and light emitting device
arrays 65, 66, and 67 by being sequentially turned on and off, a
color image can be formed without loss of light. Since the R, G,
and B color light beams proceed in the same path through the
waveguide 80, an additional optical path changer is not
necessary.
[0070] A projection system adopting the above-described
illumination system will now be described, and is shown in FIG. 10.
The projection system of FIG. 10 includes an illumination system 90
to emit a light beam, a display device 95 to form an image by using
R, G, and B color light beams emitted from the illumination system
90, and a projection lens unit 97 to project the image formed by
the display device 95 toward a screen 98. The illumination system
90, as shown in FIG. 2, includes at least one light emitting device
10 to emit a light beam having a predetermined wavelength, at least
one holographic optical element 15 to change an optical path of the
light beam emitted from the light emitting device 10, and a
waveguide 20 to guide an incident light beam input through the
holographic optical element 15.
[0071] The illumination system 90 is formed of one of the
illumination systems according to the first through third
embodiments of the present invention. Referring to FIGS. 2 and 4,
an LED (light emitting diode), an LD (laser diode), an organic EL
(electro luminescent), or an FED (field emission display) can be
used as the light emitting device or the light emitting device
array 10. The light emitting device or the light emitting device
array 10 is formed of the first, second, and third light emitting
devices or light emitting device arrays 10a, 10b, and 10c to emit
R, G, and B color light beams. To secure a sufficient amount of
light, additional ones of the light emitting devices 10a, 10b, and
10c, the holographic optical element 15, and the waveguide 20 can
be further provided in the same structure in a horizontal or
vertical direction. Here, the holographic optical element 15 can be
replaced by a diffractive optical element having the same
function.
[0072] Also, the prism array 25 to make parallel the light beam
emitted from the waveguide 20 can be provided. As described above,
the prism array 25 can be provided separate from the waveguide 20
or can be integrally formed at the exit end portion of the
waveguide 20 (please refer to FIGS. 3A through 3C). Here, a fly eye
lens 92 to uniformly distribute the R, G, and B color light beams
to proceed in the same direction through the prism arrays 25, 26,
27, and 28, and a relay lens 93 to condense the light beam toward
the display device 95, can be further provided. Accordingly, a
color image is formed by the display device 95 by using the R, G,
and B color light beams. The display device 95 can be a mobile
mirror apparatus to realize a color image by means of an on-off
switching operation of micro-mirrors according to an image signal,
or an LCD device to realize a color image by polarizing and
modulating an incident light beam.
[0073] Here, the illumination system 90 can further include an
optical path changer 30 to synthesize light beams input from
different directions by changing proceeding paths of the light
beams to proceed in a single direction. The optical path changer 30
is disposed after the prism arrays 25, 26, 27, and 28.
[0074] The optical path changer 30 can be formed of the first
through third dichroic filters 30a, 30b, and 30c to change
proceeding paths of the R, G, and B color light beams by
selectively transmitting or reflecting according to the wavelength
of each incident light beam. The R, G, and B color light beams
proceeding in the same direction through the first through third
dichroic filters 30a, 30b, and 30c are uniformly condensed by the
fly eye lens 92 and the relay lens 93 to form a color image in
conjunction with the display device 95.
[0075] Here, although the first through third dichroic filters 30a,
30b, and 30c are used as the optical path changer 30 in the above
description, the cholesteric and modulation filter 35 to transmit
or reflect an incident light beam according to the direction of
circular polarization of the light beam can also be used. Also, the
X prism 60 or X type dichroic filter can be used to change the
optical paths of the R, G, and B color light beams input from
different directions to proceed in the same direction. Here, the
first through third light emitting devices or light emitting device
arrays 10a, 10b, and 10c to emit the R, G, and B color light beams
are arranged to be separated from one another at a predetermined
angle with respect to the X prism 60 or X type dichroic filter, as
shown in FIG. 8.
[0076] In another embodiment, the illumination system 90 may
include a light emitting device or light emitting device array 40,
a focusing lens 45 to condense the light beam emitted from the
light emitting device or light emitting device array 40, and a
waveguide 50 having a reflection surface 48 inclined at a
predetermined angle so that the light beam condensed by the
focusing lens 45 is totally reflected. The second parallel beam
forming unit 55, such as a collimating lens or a Fresnel lens, to
make the light beam passing through the waveguide 50 a parallel
beam, is further provided.
[0077] The light beam made parallel by the parallel beam forming
unit 55 is made uniform by the fly eye lens array 92 and condensed
on the display device 95 by the relay lens 93. Here, since an
optical path changer such as the first through third dichroic
filters 30a, 30b, and 30c, the cholesteric band modulation filter
35 or the X prism or X type dichroic filter 60 can be inserted
after the second parallel beam forming unit 55 as described above,
a detailed description thereof will be omitted.
[0078] Also, the projection system according to the present
invention, as shown in FIG. 9, can adopt an illumination system in
which the R, G, and B color light beams incident on the waveguide
80 through the fourth through sixth holographic optical elements
75, 76, and 77 proceed in the same direction. In this case, since
the R, G, and B color light beams proceed along the same optical
path through the single waveguide 80, an additional optical path
changer is not needed. Thus, the volume of the projection system
can be reduced.
[0079] The R, G, and B color light beams emitted from the
illumination system according to the above various embodiments of
the present invention are incident on the display device 95 via the
fly eye lens 92 and the relay lens 93 to form a color image. The
color image is magnified by the projection lens unit 97 and focused
on the screen 98.
[0080] As described above, in the illumination system according to
the present invention, since a light emitting device or light
emitting device array to emit a light beam having a narrow spectrum
in a desired wavelength band is used, color purity is improved and
color gamut having a wider distribution can be secured. Since the
cross section of a light beam is reduced by the holographic optical
element or diffractive optical element and the waveguide, the
illumination system can be made compact and loss of light can be
reduced. Also, as the light beam condensed at one point by the
focusing lens proceeds through the waveguide, the cross section of
the light beam can be further reduced. Further, less heat is
generated and lifespan is lenghtened, as compared to the
conventional lamp light source.
[0081] Also, in the projection system adopting the illumination
system according to the present invention, since time sequential
driving is possible by the illumination system having a light
emitting device or light emitting device array, a color wheel is
not needed. Also, an on/off switching operation which is faster
than the rotation speed of the color wheel is possible, and thus, a
high frame rate can be realized and power consumption can be
reduced. Therefore, the projection system adopting the illumination
system according to the present invention can provide a high
resolution and high quality image.
[0082] Although a few preferred embodiments of the present
invention have been shown and described, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
invention, the scope of which is defined in the claims and their
equivalents.
* * * * *